Yes, PAWPAW is a Scrabble word!

Letter values in Scrabble US: P 3, A 1, W 4, P 3, A 1, W 4.

Is it a valid word?

PAWPAW is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

tropical American shrub or small tree having huge deeply palmately cleft leaves and large oblong yellow fruit
small tree native to the eastern United States having oblong leaves and fleshy fruit
fruit with yellow flesh; related to custard apples

Also: papaya tree, melon tree, carica papaya, papaw tree, asimina triloba.

Not playable in Scrabble US: PAPAIA.